1. Technical Field
The invention relates to an apparatus for error correction encoding a data stream of information into blocks of error correction encoded information.
2. Related Art
Such an apparatus is known from WO 96/31880. The known apparatus discloses the generation of different sync words for the sync blocks in a block of error correction encoded information. This enables the identification of the position of a sync block within a block of error correction encoded information. In spite of this, errors occur after receiving the error correction encoded information that cannot be corrected for in the error correction step normally available in the receiver.
The invention aims at improving the error correction capability. In accordance with the invention, the error correction encoder supplies one of m mutually different sync words to each of said n sync blocks in said block of error correction encoded information, such that the sequence of two sync words of two subsequent sync blocks in the block of error correction encoded information is unique for each two subsequent sync blocks in the block of error correction encoded information, m being an integer for which holds 2 less than m less than n.
The invention is based on the following recognition. Sync words used for identifying the sync blocks are generally unique bit patterns that do not occur elsewhere in the serial data stream of information. A further aim is to uniquely identify the exact position of a sync block in the array of n sync blocks in the blocks of error correction encoded information. This requires a plurality of mutually different sync words. It should further be noted that the error correction capability increases with increasing number of sync blocks in a block of error correction encoded information. Identifying each sync block separately would mean that there are as many sync words as there are sync blocks in a block of error correction encoded information. In accordance with the invention, with the requirement that the sequence of two sync words of two subsequent sync blocks in the block of error correction encoded information is unique for each two subsequent sync blocks in the block of error correction encoded information, less mutually different sync words are needed, so that more words are available for the information itself, whilst moreover improving the error correction capability.
In the invention, the error correction encoder may supply one of m mutually different sync words to each of said n sync blocks in said block of error correction encoded information, such that each time two sync words of two sync blocks in the block of error correction encoded information separated from each other by one sync block is unique for each group of two sync blocks in the block of error correction encoded information, said two sync blocks being separated from each other by one sync block, m being an integer for which holds 2 less than m less than n. This enables a reliable determination of the position of the sync block detected, even in the case that the sync word of this sync block was missed.
In the invention, the error correction encoder may supply one of m mutually different sync words to each of said n sync blocks in said block of error correction encoded information, such that each time two sync words of two sync blocks in the block of error correction encoded information separated from each other by two sync blocks is unique for each group of two sync blocks in the block of error correction encoded information, said two sync blocks being separated from each other by two sync blocks, m being an integer for which holds 3 less than m less than n. This enables a reliable determination of the position of the sync block detected, even in the case that the sync word of this sync block and the sync word of the preceding or the next sync block was missed.